This study examines the prevalence and correlates of psychiatric disorders and mental health treatment-seeking in a nationally representative sample of pregnant and postpartum women in the United States. It finds that the 12-month prevalence of psychiatric disorders among pregnant women (25.3%) and postpartum women (27.5%) is similar to that of non-pregnant women of childbearing age (30.1%), except for a significantly higher prevalence of major depressive disorder in postpartum women (9.3%) compared to non-pregnant women (8.1%). Pregnant and postpartum women had lower rates of alcohol use disorders and any substance use, except illicit drug use, than non-pregnant women. Age, marital status, health status, stressful life events, and history of traumatic experiences were all significantly associated with higher risk of psychopathology in pregnant and postpartum women. Most women with a current psychiatric disorder did not receive any mental health care in the 12-months prior to the survey regardless of pregnancy status. Pregnancy itself is not associated with increased risk of mental disorders, though the risk of major depressive disorder may be increased during the postpartum period. Young, unmarried women with recent stressful life events, complicated pregnancies, and poor overall health were at significantly increased risk of mental disorders during pregnancy. Low rates of maternal mental health care underscore the need to improve recognition and delivery of treatment for mental disorders occurring during pregnancy and the postpartum. Pregnancy and the postpartum period are widely considered periods of increased vulnerability to psychiatric disorders. Psychiatric disorders during pregnancy are associated with poor maternal health and inadequate prenatal care. Maternal psychiatric disorders during pregnancy and the postpartum period are also associated with numerous adverse outcomes for the offspring, including maladaptive fetal growth and development, poor cognitive development and behavior during childhood and adolescence, and negative nutritional and health effects. The study highlights four major results: (1) although rates of Axis I psychiatric disorders, including substance use, mood and anxiety disorders, are high in women of childbearing age regardless of pregnancy status, pregnancy per se is not associated with an increased risk of new onset or recurrence of mental disorders, and is associated with lower rates of substance use, except illicit drug use, and substance use disorders; (2) the risk of major depressive disorder may be increased during the postpartum period; (3) younger age, not being married, exposure to traumatic or stressful life events in the last 12 months, pregnancy complications, and overall poor health increase the risk of mental disorders in past-year pregnant women; and (4) treatment rates among pregnant women with psychiatric disorders are very low. The study also finds that pregnant women with psychiatric disorders seldom reported having sought mental health treatment. This result holds regardless of pregnancy status, even when adjusting for sociodemographic factors. Past-year pregnant women with past-year mood disorders had lower treatment rates than non-pregnantThis study examines the prevalence and correlates of psychiatric disorders and mental health treatment-seeking in a nationally representative sample of pregnant and postpartum women in the United States. It finds that the 12-month prevalence of psychiatric disorders among pregnant women (25.3%) and postpartum women (27.5%) is similar to that of non-pregnant women of childbearing age (30.1%), except for a significantly higher prevalence of major depressive disorder in postpartum women (9.3%) compared to non-pregnant women (8.1%). Pregnant and postpartum women had lower rates of alcohol use disorders and any substance use, except illicit drug use, than non-pregnant women. Age, marital status, health status, stressful life events, and history of traumatic experiences were all significantly associated with higher risk of psychopathology in pregnant and postpartum women. Most women with a current psychiatric disorder did not receive any mental health care in the 12-months prior to the survey regardless of pregnancy status. Pregnancy itself is not associated with increased risk of mental disorders, though the risk of major depressive disorder may be increased during the postpartum period. Young, unmarried women with recent stressful life events, complicated pregnancies, and poor overall health were at significantly increased risk of mental disorders during pregnancy. Low rates of maternal mental health care underscore the need to improve recognition and delivery of treatment for mental disorders occurring during pregnancy and the postpartum. Pregnancy and the postpartum period are widely considered periods of increased vulnerability to psychiatric disorders. Psychiatric disorders during pregnancy are associated with poor maternal health and inadequate prenatal care. Maternal psychiatric disorders during pregnancy and the postpartum period are also associated with numerous adverse outcomes for the offspring, including maladaptive fetal growth and development, poor cognitive development and behavior during childhood and adolescence, and negative nutritional and health effects. The study highlights four major results: (1) although rates of Axis I psychiatric disorders, including substance use, mood and anxiety disorders, are high in women of childbearing age regardless of pregnancy status, pregnancy per se is not associated with an increased risk of new onset or recurrence of mental disorders, and is associated with lower rates of substance use, except illicit drug use, and substance use disorders; (2) the risk of major depressive disorder may be increased during the postpartum period; (3) younger age, not being married, exposure to traumatic or stressful life events in the last 12 months, pregnancy complications, and overall poor health increase the risk of mental disorders in past-year pregnant women; and (4) treatment rates among pregnant women with psychiatric disorders are very low. The study also finds that pregnant women with psychiatric disorders seldom reported having sought mental health treatment. This result holds regardless of pregnancy status, even when adjusting for sociodemographic factors. Past-year pregnant women with past-year mood disorders had lower treatment rates than non-pregnant